Coherent synchrotron radiation (CSR) drives potentially severe degradation of beam quality when compressing a bunched electron beam. Prior art methods of bunching have been unable to avoid this problem, as all prior methods involve compressing the bunch slowly and/or traversing a large angle dipole with a short bunch. Degradation of beam quality due to these effects limits the performance of all existing designs for energy recovery linac (ERL) drivers of free electron lasers (FELs) at single bunch charges much in excess of 100 pC. Thus, driver transport system designs in which the beam undergoes either parasitic compressions or transport at short bunch lengths through large bend angles are incapable of maintaining beam quality adequate for lasing with high efficiency or at high power.
Thus, there is a need for a method of controlling coherent synchrotron radiation degradation of beam quality when a bunched electron beam is compressed in a free electron laser operation.